Fluid-tight connecting apparatus

ABSTRACT

A fluid-tight coupling (2) for connecting opposite ends of the pipe section (4, 6) to provide a fluid-tight AI seal is described. The fluid-tight seal between the upper and lower tubular sections is provided by an upper and a lower metal-to-metal seal produced respectively between a lower sealing surface (10) of the upper pipe section (4) and an upper sealing surface (12) of an annular interface member (8) and an upper sealing surface (14) of the lower section (6) and a lower sealing surface (16) of the annular interface member (8). The metal-to-metal seals are produced and maintained by a collar (20) arranged coaxially about the coupling region of the tubular sections. The collar (20) is coupled by threads (24, 26) to the upper and lower pipe sections and rotation of the collar (20) in one direction brings the sections (4, 6) together comprising the interface member (8) and deforming at least one sealing surface of each pair of sealing surfaces (10, 12) and (14, 16) to increase the contact area and provide metal-to-metal seals. Embodiments and applications of the invention are described.

FIELD OF THE INVENTION

This invention relates to fluid-tight connectors and in particular,though not necessarily, to wireline type fluid-tight connectors forproviding metal-to-metal seals between opposed ends of tubes making up apressure bearing string.

BACKGROUND OF INVENTION

A known type of fluid-tight connector means for connecting togetheropposite ends of two pipes, or tubes, comprises flanges provided on theends of the pipes to be joined. A fluid-tight seal between the tubes maybe obtained by bolting the flanges together around the circumference ofthe pipes. It is difficult and time consuming, however, to provide acircumferentially uniform seal with such an arrangement and, in order toimprove the uniformity, it is common to insert an annular elastomericgasket between the opposed flanges. It is often undesirable, however, touse elastomeric gaskets in hostile environments, such as those involvinghigh temperatures, high pressures, or corrosive fluids in which they arelikely to quickly decompose. In such hostile environments it isnecessary to rely only upon metal-to-metal seals and to accept the abovementioned disadvantages.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is providedcoupling means for enabling the fluid-tight coupling of opposed ends offirst and second substantially tubular members by means of a pair ofmetal-to-metal seals, the coupling means comprising first and secondmetal sealing surfaces extending circumferentially around end regions ofthe first and second tubular members respectively, and a substantiallyannular interface member having circumferentially extending and axiallyspaced third and fourth metal sealing surfaces, the interface memberbeing arranged in use between the coupling ends of the tubular membersso that, with substantially no force being applied between member, saidfirst and second sealing surfaces oppose, but are not aligned with,respective ones of the third and fourth sealing surfaces, the couplingmeans further comprising means for forcing said opposed ends of thetubular members together in a sense tending to compress the interfacemember, wherein at least one sealing surface of each pair of opposedsurfaces is of a metal which is deformable under the action of theforcing means so as to increase the area of contact between the sealingsurfaces of each pair of opposed surfaces, thereby to provide saidmetal-to-metal seals.

In a preferred embodiment of the invention, the sealing surfaces of thetubular members and of the interface member are arranged so that in usethey do not lie in a plane perpendicular to the direction of the forceapplied by the forcing means. The sealing surfaces of each pair ofopposed surfaces are misaligned in use, prior to compression, by lessthan 5°, preferably by less than 1.5° and more preferably still byapproximately 0.50°. Compression of said deformable metal forces saidadjacent surfaces substantially into alignment.

Preferably, said sealing surfaces are frustoconical. Preferably, theinterface member is comprised of said deformable material. It will beclear, however, that the portion of the tubular members providing thefirst and second sealing surfaces could alternatively comprisedeformable metal or that both these portions and the interface membercould comprise deformable metal. Said deformable metal is preferably analloy containing copper/beryllium, phosphor/bronze, or aluminium/bronze.

Preferably, the force applying means is arranged to distribute theapplied force evenly around the circumferences of the tubular members,for example by engaging one or both of the tubular members by way of ascrew thread.

Preferably, the force applying means comprises a substantiallycylindrical collar for positioning coaxially around the opposed ends ofthe tubular members to be coupled. The collar is arranged to moveablyengage at least one of said opposed ends, for example by means of anaxially extending screw thread. Preferably, the collar moveably engagesboth of the opposed ends by means of axially extending, but oppositelydirected, screw threads so that rotation of the collar about the tubularmember forces said opposed ends together. Rotation of the collar may beachieved, for example, by means of a ratchet type tool arranged to belocated in a locating recess on the collar and to engage teeth spacedaround a circumferential region of one of the tubular members or aroundan intermediate surface mounted thereon.

It will be apparent that embodiments of the invention may provide aconnector which makes use of metal-to-metal seals and which can be usedto quickly connect and disconnect tubular members. Moreover, themetal-to-metal seals may be achieved uniformly around the circumferenceof the connection. Such connectors are particularly suitable for use inhostile environments, especially in high pressure/high temperature oilwells.

According to a second aspect of the present invention there is provideda method of coupling together opposed ends of first and secondsubstantially tubular members to provide a fluid tight seal therebetweenby way of a pair of metal-to-metal seals, the method comprising:

providing first and second metal sealing surfaces extendingcircumferentially around end regions of the first and second tubularmembers respectively;

axially aligning said opposed ends of the first and second tubularmembers, providing a substantially annular interface member havingcircumferentially extending and axially spaced third and fourth metalsealing surfaces;

disposing the interface member between said opposed ends of the tubularmembers so that the interface member is axially aligned with the tubularmembers and so that the first and second sealing surfaces oppose, butare not aligned with, respective ones of the third and fourth sealingsurfaces; and

forcing said opposed ends together in a sense tending to compress theinterface member, at least one sealing surface of each pair of opposedsurfaces being of a metal which is deformable under the influence of theforcing action so as to increase the area of contact between the sealingsurfaces of each pair of opposed sealing surfaces, thereby to providesaid metal-to-metal seals.

Preferably, the step of forcing the opposed ends of the tubular memberstogether comprises the step of arranging a substantially cylindricalcollar coaxially around the opposed ends, so as to engage axiallyextending screw threads provided on both said opposed ends, and rotatingthe collar around the opposed ends. Rotation of the collar may beachieved by means of a mechanical advantage tool acting between thecollar and one of the opposed ends.

According to a third aspect of the invention there is provided a methodof coupling together opposed ends of first and second substantiallytubular members to provide a fluid tight seal therebetween by way of apair of metal-to-metal seals, the method comprising the steps of:

axially aligning said opposed ends of the tubular members so that theyare spaced apart;

disposing a deformable interface member between the opposed ends so thatfirst and second metal sealing surfaces, extending circumferentiallyaround end regions of the first and second tubular members respectively,abut, but are not aligned with, respective ones of third and fourthcircumferentially extending and axially spaced metal sealing surfaces ofthe interface member; and,

forming said pair of metal-to-metal seals by converting a rotationalmotion about the common axis to an axial compressive force thereby todeform the interface member to bring the sealing surfaces of the twopairs of abutting sealing surfaces into alignment.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will become apparent from thefollowing description when taken in combination with the accompanyingdrawings in which:

Fig. 1 shows an axial cross-sectional view of a connection means forconnecting two tubular sections of a drill string;

FIG. 1a shows a detail of FIG. 1; and

FIG. 2 shows a transverse cross-sectional view of the connection meansof FIG. 1 taken on the line A—A.

FIG. 1 shows a cross-sectional view of a coupling means for enabling thefluid-tight coupling of an upper and a lower tubular section 4,6, bothsections having a generally circular cylindrical construction as shownin FIG. 2. A plurality of tubular sections may be coupled, end to end,in like manner to form, for example, a test string for location in awellbore. In particular, the fluid-tight seal between the upper andlower tubular sections is provided by an upper and a lowermetal-to-metal seal produced respectively between a lower sealingsurface 10 of the upper section 4 and an upper sealing surface 12 of anannular interface member 8 and an upper sealing surface 14 of the lowersection 6 and a lower sealing surface 16 of the annular interface member8. The metal-to-metal seals are produced and maintained by a collar 20arranged coaxially about the coupling region of the tubular sections.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Considering the coupling region in more detail, the lower sealingsurface 10 of the upper section 4 is a frustoconical surface provided bya chamfered edge which is oriented at an angle of approximately 30° withrespect to the central axis of the upper section and which extendscircumferentially around the inside lower end of the upper section. Thelower section 6 is provided at its upper end with a cylindricalreceiving section 13 of reduced thickness. A strengthening section 15 ofenlarged thickness is provided between the receiving section and themain body 17 of the lower section. A chamfered edge, similar to thatprovided on the upper section 4, is formed on the shoulder between thereceiving section 13 and the strengthening section 15 to provide afrustoconical surface forming the upper sealing surface 14 of the lowersection 6. A screw thread, indicated generally by reference numeral 24,is provided on the outer surface of the lower section 6 and extendsaxially from the top of the receiving section 13 to a position part wayalong the strengthening section 15.

The annular interface member 8 is provided by a short cylindrical memberwhose inside diameter is approximately equal to the inside diameter ofthe tubular sections. The outer, upper and lower edges of the annularinterface member are chamfered to provide upper and lower frustoconicalsealing surfaces 12,16 which extend circumferentially around theinterface member.

FIG. 1a shows an enlarged detail of the region “X” shown dotted in FIG.1. As will be seen, the upper and lower sealing surfaces of theinterface member 8 are oriented at an angle with respect to the centralaxis of the interface member so that when the interface member iscoaxially arranged between the ends, and with no force being appliedacross the boundary between the sealing surfaces of the interface memberand of the upper and lower sections, the two pairs of opposed surfacesdiverge from the interior surface at an angle of approximately 0.5°.

Whilst the upper and lower sections 4,6 are of a substantiallynon-compressible metal, for example stainless steel, the interfacemember 8 is of a compressible metal alloy, for example copper/beryllium,phosphor/bronze or aluminium/bronze.

The coupling means 2 is provided with a force applying mechanism forforcing the upper and lower sections together in a sense tending tocompress the interface member 8. The force applying mechanism comprisesa substantially cylindrical collar 20 which is provided on its lowerinternal surface with a first screw thread, generally indicated byreference numeral 24′, which extends axially from the bottom of thecollar to a position approximately midway along the collar. The collarfor engagement with screw thread 24 is also provided with a second screwthread, generally indicated by reference numeral 26, on its upperinternal surface, which extends axially from the top of the collar to aposition approximately a quarter of the way long the collar. Acylindrical bearing 22 is arranged coaxially about the end of the uppersection 4 with its axial position being maintained by the engagement ofthe lower edge of the bearing with a supporting shoulder 23 whichprojects outwardly from, and extends circumferentially around, the uppersection. The bearing 22 is free to rotate about the upper section 4 andis provided on its outer surface with a screw thread 26′ which extendsaxially from a position near the bottom of the bearing to a positionjust over midway along it. In order to couple the upper and lowersections together, the lower section 6 is first secured in an uprightposition. The interface member 8 is then coaxially positioned inside thelower section through its upper opening so that the lower frustoconicalsealing surface 16 of the interface member 8 contacts the frustoconicalsealing surface 14 of the lower section. It will be appreciated from aconsideration of FIG. 1a that the initial area of contact between theadjacent sealing surface is small and comprises only a substantiallycircular contact zone.

The upper section 4 is then axially aligned above the opening in thelower section 6 and is lowered until its frustoconical sealing surface10 contacts the upper frustoconical sealing surface 12 of the interfacemember 8, again over a substantially circular contact zone. The bearing22 is generally arranged about the upper section prior to the loweringof the upper section.

The collar 20 is then lowered over the upper section. The collar isarranged so that its lower screw thread is recessed slightly into itsinner wall thereby allowing the collar to pass freely over the bearing22 until the lower screw thread of the collar engages the correspondingscrew thread provided on the outer surface of the lower section.

With reference to FIG. 2 of the drawings, which shows a cross-sectionalview of the coupling means taken on a line A—A of FIG. 1, the forceapplying mechanism is operated by means of a ratchet type tool 30, orother force multiplying tool which makes use of mechanical advantages,which is secured in one of four recesses 34 spaced at 90° intervalsaround the upper surface of the collar 20. The ratchet 30 is providedwith a circular end piece in which are formed a plurality of teeth 32spaced so as to engage similarly spaced teeth 28′ providedcircumferentially around the outer surface of the bearing 22. Theratchet is manually rotated about the central axis of the recess in thedirection indicated by the arrow in FIG. 2. Movement in this directioncauses the collar to screw down over the lower section 6.

The screwing down of the collar over the lower tubing string continuesuntil the upper screw thread 26 provided on the inner surface of thecollar engages the corresponding screw thread 26′ provided on the outersurface of the bearing 22. The two pairs of screw threads 24, 24′ and26, 26′ are arranged so that continued action by the ratchet in theindicated direction, in addition to drawing the lower section upwardsrelative to the collar, causes the upper section to move downwardlyrelative to the collar. Thus, the upper and lower sections are drawntogether in a sense tending to compress the interface member 8. As theforce applied across the two pairs of adjacent sealing surfacesincreases, the interface member 8, which is of a compressible metalalloy, is compressed with the result that the two pairs of opposedsealing surfaces are forced together. The ratchet action is continueduntil metal-to-metal seals of appropriate extent are obtained. It willbe appreciated that the force applied across the sealing surface issubstantially uniformly distributed around the circumferences of theseals thus reducing the risk that the tubes will be misaligned.

The point at which appropriate seals are obtained can be determined by anumber of known techniques: for example, by pressure testing the seal orby means of a force gauge on the ratchet.

It is envisaged that, instead of producing the alignment of adjacentsealing surfaces by use of a compressible metal, alignment may beenabled by forming at least one surface of each pair of adjacentsurfaces so as to be deflectable under the application of forcesproduced by the force applying mechanism.

The coupling means additionally comprises an elastomeric O-ring 18located in a circumferentially extending recess in the outer surface ofthe upper section. The O-ring projects sufficiently from the recess tocontact the inner surface of the receiving section of the lower section.The O-ring serves as a secondary fluid seal means which is normallyisolated from the fluid flowing through the tubing strings but whichserves to prevent fluid leakage in the event that the metal-to-metalseals fail or are loosened. The coupling means described above has beendescribed in general terms and it will be appreciated that it can beused in a wide range of applications where metal-to-metal seals arerequired. It is envisaged that a particular application is in the areaof wellbore tools for siting in high pressure/high temperature (HPHT)oil wells.

The embodiments described above are for the purpose of illustration andit will be apparent that variations may be made within the scope of theinvention. For example, the seals may be engaged by means of anelectrically or hydraulically operated tool rather than by means of amanually operated tool.

What is claimed is:
 1. Coupling means for enabling the fluid-tightcoupling of opposed ends of first and second substantially tubularmembers by means of a pair of metal-to-metal seals, the coupling meanscomprising first and second metal sealing surfaces extendingcircumferentially around respective coupling ends of the first andsecond tubular members respectively, and a substantially annularinterface member having circumferentially extending and axially spacedthird and fourth metal sealing surfaces, the interface member beingdisposed between the coupling ends of the tubular members so that, withsubstantially no force being applied between the tubular members and theinterface member, said first and second sealing surfaces oppose, but arenot aligned with, respective ones of the third and fourth sealingsurfaces, the coupling means further comprising means for forcing saidcoupling ends of the tubular members together to compress the interfacemember therebetween, said means for forcing comprising a substantiallycylindrical collar positionable coaxially around the coupling ends ofsaid tubular members for engagement with a first of said members, and abearing disposed coaxially between said collar and a second of saidtubular members, said bearing having an outer surface provided with aplurality of teeth for engagement with mating teeth of a ratchet, saidbearing being operative to distribute applied force evenly around thecircumferences of the tubular members by engaging said second of thetubular members by way of a first axially extending screw thread,wherein at least one sealing surface of each pair of opposed surfaces isof a metal which is deformable under action of the forcing means so asto increase an area of contact between the sealing surfaces of each pairof opposed surfaces, thereby to provide said metal-to-metal seals. 2.Coupling means as claimed in claim 1 wherein the sealing surfaces of thetubular members and of the interface member are arranged so that in usethey do not lie in a plane perpendicular to the direction of the forceapplied by the forcing means.
 3. Coupling means as claimed in claim 1wherein the sealing surfaces of each pair of opposed surfaces aremisaligned in use, prior to compression, by an angle which ranges from5° to approximately 0.5°.
 4. Coupling means as claimed in claim 1wherein said sealing surfaces are frustoconical.
 5. Coupling means asclaimed in claim 1 wherein the interface member is comprised of saiddeformable metal.
 6. Coupling means as claimed in claim 1 wherein therespective end regions of the tubular members providing the first andsecond sealing surfaces comprise deformable metal and the interfacemember comprises deformable metal.
 7. Coupling means as claimed in claim1 wherein said deformable metal is an alloy of copper/beryllium,phosphor/bronze or aluminium/bronze.
 8. Coupling means as claimed inclaim 1 wherein the collar moveably engages said first of said tubularmembers by means of an axially extending second screw thread. 9.Coupling means as claimed in claim 8 wherein said first and second screwthreads axially extend in opposite directions such that rotation of thecollar about the tubular member forces said coupling ends together. 10.A method of coupling together opposed ends of first and secondsubstantially tubular members to provide a fluid tight seal therebetweenby way of a pair of metal-to-metal seals, the method comprising:providing first and second metal sealing surfaces extendingcircumferentially around end regions of the first and second tubularmembers respectively; axially aligning said opposed ends of the firstand second tubular members, providing a substantially annular interfacemember having circumferentially extending and axially spaced third andfourth metal sealing surfaces; disposing the interface member betweensaid opposed ends of the tubular members so that the interface member isaxially aligned with the tubular members and so that the first andsecond sealing surfaces oppose, but are not aligned with respective onesof the third and fourth sealing surfaces; disposing a cylindrical collarcoaxially around the tubular member end regions for engagement with afirst of said tubular members and a bearing coaxially between saidcollar and a second of said tubular members, said bearing having anouter surface provided with a plurality of teeth for engagement withmating teeth of a ratchet and being engageable with said second tubularmember by way of a first axially extending screw thread; and ratchetingsaid bearing to force said opposed ends together to compress theinterface member therebetween, at least one sealing surface of each pairof opposed surfaces being of a metal which is deformable under theinfluence of the forcing action so as to increase an area of contactbetween the sealing surfaces of each pair of opposed sealing surfaces,thereby to provide said metal-to-metal seals.
 11. A method as claimed inclaim 10 wherein the collar movably engages said first tubular member bymeans of an axially extending second screw thread, said first and secondscrew threads extending in opposite axial directions, and the step offorcing the opposed ends of the tubular members together comprises thestep of disposing said substantially cylindrical collar coaxially aroundthe opposed ends and rotating the collar around the opposed ends.